A stranded Greenland shark found off the coast of Cornwall died from meningitis, according to a postmortem examination, providing what is believed to be the first evidence of the disease in the species.
The 4-metre long shark, thought to be about 100 years old, was first discovered by a dog walker on 13 March on a beach near Penzance but was washed back into the sea before it could be properly examined. After a two-day search it was discovered floating in the water off Newlyn harbour beach by a tourist boat and a postmortem was carried out.
Greenland sharks live up to 2,600 metres below the surface of the Arctic and north Atlantic oceans. Pathologists believe meningitis explains why this female was out of her natural deep-water habitat. Her brain was slightly discoloured and congested with a cloudy fluid, which contained a type of bacteria called Pasteurella, likely to have caused the meningitis. It is not known how the shark got the infection.
The last time a Greenland shark washed up in the UK was in Northumberland in 2013. The discovery of this specimen has given researchers an opportunity to study the planet’s longest-lived vertebrate species – some are thought to be more than 400 years old. Despite probably being born just after the first world war, this shark was still considered a juvenile. Females are thought to reach maturity at 150 years old, when they are about 4.2 metres long.
“This unfortunate and extraordinary stranding has allowed us to get an insight into the life and death of a species we know little about,” said Rob Deaville from Zoological Society of London’s (ZSL) Cetacean Strandings Investigation Programme (CSIP). “It’s almost certainly the oldest animal I’ve ever seen.
“With only a small handful of Greenland shark strandings previously recorded in the UK, this likely represents the first necropsy ever carried out on this species in this country and was an exceptional opportunity to learn more about the life and death of this cryptic and endangered deep-water shark,” he said.
Meningitis is caused by a viral or bacterial infection. The same Pasteurella bacteria has been found to cause meningitis in humans but it is extremely rare. Pathologists do not yet know what species of Pasteurella affected the shark and will investigate further. Meningitis has been described before in sharks but it is not known how widespread it is, said Deaville. He has seen a couple of beached basking sharks affected over the past decade, and it has also been reported in captive lemon sharks.
The postmortem was carried out by the Cornwall marine pathology team, which is part of CSIP. Pathologists began with an external examination to look for a possible cause of death, such as net marks or parasites. Then they opened up the body to access the organs, examining each one for evidence of abnormalities. Samples were taken, documented, and sent for detailed analysis, looking, for instance, at diet, exposure to pollution and disease.
Pathologist James Barnett, who carried out the postmortem with a team of volunteers, said: “The shark’s body was in poor condition and there were signs of a haemorrhage within the soft tissue around the pectoral fins which, coupled with the silt found in her stomach, suggested she may well have live stranded.
“As far as we’re aware, this is one of the first postmortem examinations here in the UK of a Greenland shark and the first account of meningitis in this species.”
The shark was dissected and body parts have been sent to research institutions around the country for examination.
Research into its skin will examine the evolution of how the sharks swim. Its gastrointestinal tract will reveal if there are microplastics present, and scientists will look at other hard remains such as fish ear bones, or squid beaks, which could shed light on the shark’s diet. Toxicology tests on its liver could reveal what pollutants the shark was exposed to during its long life.
Some samples, kept at -80C, are being sent to the Sanger Institute to have the whole genome sequenced as part of the Darwin Tree of Life project, where they could inform research on cancer and ageing.
Greenland sharks are the only shark species hardy enough to spend all year in the Arctic Ocean. Their very slow metabolism means they are well adapted to cold water, and may also explain their long lifespan. They grow less than 1cm a year, have a top speed of just 2.9km an hour and a heart that beats five or six times a minute. The largest specimen ever found was a 5-metre female between 272 and 512 years old.
“I’ve been doing this job for 25 years and we get a lot of strandings, but I certainly wasn’t expecting a call about a Greenland shark on a Sunday afternoon – we were a bit dumbfounded,” said Deaville. “There is so much that is weird and wonderful about them.”
Greenland sharks were once hunted for their liver oil but now many end up caught in fishing nets. The species is listed as vulnerable. CSIP has done postmortems on 4,500 cetaceans over 30 years, making it one of the world’s largest databases on strandings and causes of mortality.
The stranded shark was spotted by Rosie Woodroffe, a biologist from ZSL, who was out walking her dog. “I thought immediately that it looked like a Greenland shark but, not being a shark expert, assumed I must be mistaken and reported it to the marine strandings network as a presumed basking shark.”
When she got home she dug out a book on sharks and realised what she had found. “I can’t stop thinking about this Greenland shark, recovered dead from the sea this evening,” she later wrote on Twitter. “Even if she was ‘only’ just over 100 years old, she has shared the Earth with thylacines and passenger pigeons. She swam calmly in the deep ocean as wars raged above her.”
CSIP urges anyone who spots a stranding to call the national hotline number on 0800 652 0333. A research paper examining the shark’s postmortem investigations will be published.
Find more age of extinction coverage here, and follow biodiversity reporters Phoebe Weston and Patrick Greenfield on Twitter for all the latest news and features
